Three wire electrical plug

ABSTRACT

AN ELECTRICAL PLUG WITH A GROUND WIRE CONNECTED TO AN ANGULATED GROUNDING STRIP MOULDED INTO THE PLUG BODY BETWEEN THE TWO CONTACTS AND EXTENDING ON BOTH SIDES OF THE BODY SO THAT IT GROUNDS TO A SHROUD SHEILDING THE PINS OF A HEATER TO WHICH THE PLUG IS CONNECTED.

Sept. 20, 1971 L- E. WINDSOR THREE WIRE ELECTRICAL PLUG Filed May 16, 1969 FIG. l3

FIG. ll

INVENTOR 47! Mzvosae BY [awn/M ATTORNEY 3,606,155 THREE WIRE ELECTRICAL PLUG Lynne E. Windsor, Winnipeg, Manitoba, Canada, assignor to James B. Carter Limited, Winnipeg, Manitoba, Canada Filed May 16, 1969, Ser. No. 825,208 Int. Cl. Hlr 3/06 U.S. Cl. 339-14R Claims ABSTRACT OF THE DISCLOSURE An electrical plug with a ground wire connected to an angulated grounding strip moulded into the plug body between the two contacts and extending on both sides of the body so that it grounds to a shroud shielding the pins of a heater to which the plug is connected.

This invention relates to new and useful improvements in three wire electrical plugs designed primarily for use with 110 volt immersion heaters for automobile engines.

However, the foregoing is not to be construed as limiting as of course it will be appreciated that the plug can be used for any form of electrical connection wherein the plug-in portion engages within a socket having a grounded wall or portion therearound.

Conventionally, such heaters are plugged into an outside 110 volt socket and connect to an immersion heater within the cylinder block.

At present such connections are not grounded or three wire connections but merely two wire connections.

For reasons of safety, it is becoming desirable to insist upon all such immersion heaters and the like being grounded so that three wire extension cords and plugs will be necessary.

Inasmuch as the extension cord from the heater to the exterior of the car is detachable for manufacturing and other reasons, it is somewhat difiicult to ensure a three wire connection without enlarging the plug-in receptacle on the heater plug.

These receptacles are relatively small due to the relatively small size of the plug and the present invention provides a three wire grounded connection without increasing the size of the receptacle and in fact, without redesigning existing immersion heaters.

Conventionally, said immersion heaters are provided with male connecting posts and the end of the line cord connecting to the immersion heater terminates in a female plug engageable over said posts. These posts are conventionally shrouded by a metallic shroud forming part of the body of the heater in order to prevent damage from occurring to the pins and also in order to prevent inadvertent displacement of the plug from the heater so that this shroud provides a convenient ground contact for a three wire conduit.

The plug-in connector portion connected to the one end of the line cord is provided with an angulated grounding strip moulded into the connecting portion between the two sockets and having wings extending upon each side of the connecting portion so that when the connecting portion is engaged over the pins of the heater, the wings engage the walls of the shroud. This ground connector strip is electrically connected to a ground wire of the conduit which in turn, of course, is connected to the ground of the source of electrical supply thus grounding the heater every time it is plugged in.

Another object of the invention is to provide a device of the character herewithin described in which the ground strip can be moulded into position without increasing the size of the connector portion of the plug.

A yet further object of the invention is to provide a United States Patent 0 ii ce 3,606,l55 Patented Sept. 20, 1971 device of the character herewithin described which lends itself particularly to the use of the flat three conductor cable presently used.

A still further object of the invention is to provide a device of the character herewithin described which is simple in construction, economical in manufacture, and otherwise well suited to the purpose for which it is designed.

With the foregoing in view, and such other or further purposes, advantages or novel features as may become apparent from consideration of this disclosure and specification, the present invention consists of, and is hereby claimed to reside in, the inventive concept which is comprised, embodied, embraced, or included in the method, process, construction, composition, arrangement or combination of parts, or new use of any of the foregoing, of which concept, one or more specific embodiments of same are herein exemplified as illustrative only of such concept, reference being had to the accompanying figures in whfch:

FIG. 1 is an isometric view of the plug secured to the end of a conductor cable.

FIG. 2 is a top plan view of FIG. 1 reduced in scale.

FIG. 3 is a view similar to FIG. 2 but showing an alternative embodiment.

FIG. 4 is an enlarged isometric view of one embodiment of the ground strip per se.

FIG. 5 is a section along the line 5-5 of FIG. 1.

FIG. 6 is a front elevation of a heater plug showing the plug in position but sectioned for clarity.

FIG. 7 is a view similar to FIG. 4 but showing means to ensure angulation at the desired locus.

FIG. 8 is a front elevation of a ground strip before angulation showing an alternative method of ensuring angulation at the desired locus.

FIG. 9 is a section along the line 9-9 of FIG. 8.

FIG. 10 is a front elevation of a blank forming an alternative type of ground strip.

FIG. 11 is an isometric view of the blank of FIG. 10 formed into the ground strip.

FIG. 12 is the ground strip of FIG. 11, shown in isometric form but with the plastic plug removed.

FIG. 13 is a side sectional elevation of the completed plug with the ground strip of FIG. 11 incorporated therein.

In the drawings like characters of reference indicate corresponding parts in the difierent figures.

Proceeding therefore to describe the invention in detail, reference character 10 illustrates the plug generally formed from moulded resilient material such as rubber or plastic.

This plug is moulded upon the end of a three wire electrical cable 11 which s covered with insulation 12 and includes an outer pair of wires 13 and a central ground wire 14. This particular cable is relatively flat in configuration and therefore is suited for use with immersion heaters and the like,

The plug 10 includes the cable receiving portion 15 which in turn connects to a main body portion 16 having a substantially rectangular connecting portion 17 moulded integrally therewith and extending substantially at right angles to the cable receiving portion 15 as clearly shown.

A pair of sockets 18 are moulded integrally with the portion 17 and extend downwardly to be connected electrically with the wires 13 in the usual manner, said connection not being shown in the accompanying drawings.

Also moulded integrally within the plug-in connecting portion 17 is a ground strip collectively designated 19. This is metallic and is angulated to the preferred shape shown in FIG. 4, and defined as Z-shaped. The central plate portion 20 extends through the connecting portion 17 between the sockets 1-8 as clearly shown and is secured by the moulding process. The wings or outer panels 21 of this ground strip lie against each of the side walls 22 of the connecting portion 17 as shown in FIG. 2.

Alternatively, the ground strip 19 may be angulated to form a U-shaped member as shown in FIG. 3, once again with the central panel 20 passing through and being firmly secured within the connecting portion 17 between the wings 21 lying against the (walls 22 of the connecting portion, but towards one of the sockets 18 as clearly illustrated.

FIG. 6 illustrates generally an immersion type heater collectively designated 23 having connector pins 24 extending therefrom, said connector pins being protected by substantially rectangular shaped shroud or shield 25 formed integrally with the heater 23 and extending from the outer face 26 thereof. The dimensions of the connector portion 22 are similar to the internal dimensions of the shield 25 so that this connector portion may be inserted within this shield with the sockets 18 engaging over the pins 24 thus making electrical contact with the immersion heater element (not illustrated).

The wings 21 of the ground strip therefore engage the inner surfaces of the walls 27 of the shield as clearly shown and as these walls are formed integrally with the body of the heater, ground contact is provided and maintained.

In order to ensure good ground contact, the wings preferably should stand slightly away from the walls 22 of the connecting portion and to ensure this, I may provide pads 28 as shown in FIG. 5 formed integrally with the walls of the connecting portion 17 under the wings 21 thus forcing the wings to stand slightly away from the surfaces of the walls and ensuring good electrical contact with the walls 27 of the shield 25.

Proceeding to describe FIGS. 7 to 13 inclusive, reference should first be made to FIG. 7. It is obviously desirable to ensure a relatively sharp angulation along the lines indicated by reference character 29. It is also desirable to ensure that these angulations occur when desired, after the ground strip 19 has been moulded into the plug body.

FIG. 7 shows one method in which small apertures 30 are stamped along the line of angulation thus weakening this line and ensuring angulation occurring at the point.

FIG. 8 shows an alternative method known as knifeedge coining and indicated by reference character 31. These are score marks as shown in FIG. 9 reducing the thickness of metal along the desired bending lines, once again ensuring clean angulation along the lines desired.

FIGS. 10 to 13 inclusive show an alternative embodiment in which the ground strip is collectively designated by the reference character 32. It is preferably formed from a planar blank 33 stamped from spring bronze or brass material or similar suitable material. It comprises a substantially rectangular upper portion 34 and a bifurcated lower portion 35, said bifurcation being caused by a slit 36 extending from the lower end 37 to a circular cutout 38 which ensures that the material does not fracture beyond this point. The upper portion 34 is formed in a cylindrical configuration as indicated by reference character 34 in FIG. 11. This brings the two side lwings or strips 29 in face to face relationship as clearly shown in FIG. 11. The end 40 of the ground wire 41 is stripped and inserted within this cylindrical portion 34' which is then crimped into position as indicated by reference character 42 thus ensuring mechanical and electrical connection between the ground wire 41 and the ground strip 32.

The ground strip and conduit is then inserted within a mould (not illustrated) and plastic injected therearound thus forming the plug. It should be noted that the side wings or strips 39 extend beyond the mould and hence beyond the distal end 43 of the plug 44.

These wings or strips 39 are then bent around the distal end in opposite directions from one another to lie slightly spaced from the sides 45 of the plug 44 as clearly shown in FIG. 13.

In operation, of course, it may be inserted within the heater socket in the usual Way with the wings 39 contacting the grounded walls of this socket.

Various modifications can be made within the scope of the inventive concept which is herein disclosed and/or claimed.

What I claim as my invention is:

1. A grounded connector plug for use with an electrical appliance which has a pair of connector pins surrounded by a metallic shield, said connector plug comprising a block-shaped body.of insulating material having an end surface and at least one pair of opposite side surfaces, a pair of spaced connector pin receiving sockets embedded in said body, said sockets having open ends at said end surface of the body, and a metallic ground strip having a central portion embedded in said body in the space between said sockets and extending parallel to and coextensive with said sockets from one of said side surfaces to the other, said strip also including a pair of wing portions integral with opposite side edges of said central portion, said wing portions being superposed on the respective opposite side surfaces of said body for contact with a pin surrounding shield of an appliance.

2. The connector plug as defined in claim 1 which is further characterized in that said win-g portions are fiat and disposed in planes normal to said central portion of said strip.

3. The connector plug as defined in claim 1 wherein said wing portions extend from said central portion in opposite directions.

4. The connector plug as defined in claim 1 wherein said wing portions extend from said central portion in the same direction.

5. The connector plug as defined in claim 1 together with raised pads provided on the opposite side surfaces of said body and underlying the respective wing portions.

References Cited UNITED STATES PATENTS 2,170,131 8/1939 Doremus 33959(R) 2,406,079 8/1946 Krueger 339276(S) 3,439,308 4/1969 Swartout 339l4(R) FOREIGN PATENTS 1,074,111 1/1960 Germany 339--14(R) 483,067 7/1936 Great Britain 339'-l4(R) ERNEST R. PUR'SER, Primary Examiner R. A. HAFER, Assistant Examiner 

